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- - 225/45/17 on stock 7" wheels? (https://www.ft86club.com/forums/showthread.php?t=6949)

225/45/17 on stock 7" wheels?

Feedback from other autocrossers and trackrats most appreciated.

I'm thinking of taking advantage of the Discount Tire deal and picking up some Star Specs to run in RTR, and I was thinking - why not go with 225 instead of 215.

That in mind, have any of you tried putting 225s on 7" wide wheels? Or does that seem...non-optimal in practice?

quoting myself from an older thread:

Quote:

Originally Posted by jdrxb9 (Post 193676)

None of the rim width range specs for the 'extreme performance' 'street' tires (R-S3, AD08, R1R, XS, RE-11, Z1SS, 595RS-R) show a 7" wheel for anything wider than 225 (unless there is something wierd in non-17" or non ~25" OD I didn't look at).

Some more food for thought from multi-time SCCA champion Andy Hollis quoted from his FAQ here: http://www.cicenet.net/showthread.php?t=11708 (the original page is maintained on FB, which I won't link to : )

Quote:

Optimal wheel size
Many folks entering the ST category are refugees from Stock looking to make some performance upgrades to their car and/or reduce their tire budget. Unfortunately, they carry with them some baggage on concepts that may work well in Stock, but not in ST. One of these is optimal wheel/tire fitment.

Since Stock limits you to the OE wheel sizing, astute competitors have learned how to stuff increasingly wider tires onto those skinny rims. And tire makers have been happy to make wider and wider tires, likewise charging more and more money. But, is wider better? In Stock, the answer is often "yes". The sidewalls on these DOT-approved "Not for Highway Use" R-comps are super stiff and allow for "overtiring" much in the way that a cantilever style slick works to get around wheel width limitations for formula cars.

In ST, drivers in most classes have limits on both wheel width and tire section width, both of which are much wider than OE. The tendency is to cram the widest legal tire on the widest legal rim that will fit and go for it. But that is not always the optimal solution, as street tires do not have the same super-stiff sidewalls as do the best R-comps. Sometimes it makes sense to run a narrower tire for a given rim fitment. From the testing we've done, we find that a good rule of thumb is that the optimal rim is the same size (rounded up to the nearest half-inch or so) as the tread width (not section width!). So a 205/50-15 tire with a typical tread width of 7.5" is best on 7.5" rim. An 8" rim will work, too, but it will be majorly stretched on a 9. Likewise, it will lose some performance on a 7, and will lose a LOT going down to a 6 or 6.5. Similarly, a 225/45-15 with an 8.2" tread width works best on at least an 8.5" rim and loses a fair bit on a 7.5".

A practical example of this is in STC, STF and STS where the rim limitation of 7.5" keeps the 195/50-15 Toyo R1R at the top despite it not being the widest allowed tire size. The 225/45-15 R-S3 mounted on that same 7.5" rim is not quite as fast. But put that same R-S3 on an 8 and it comes alive. And it's even better on something a bit bigger. So in STR, where wider rims are allowed, the common 225 R-S3 on 9's is a faster combo than the 195 R1R on a 7.5 (assuming nominal weather). And putting the 195 on an 8 or wider does nothing to enhance performance and close the gap.

Ha you reposted my cicinet thread posting. I was just about to post the driect link to Hollis facebook tire thing. https://www.facebook.com/HollisRacin...45008598916447

I run both 225 star specs and 225 RS3s on a 17x7 rim. Rs3s are cheaper. And are stronger in the heat. They take the heat and just keep getting more grip. You wont be gaining anything running 225 over 215 with that rim but you wont be loosing anything either.

I ran star specs till my hankooks came in two weeks ago. And will run them again once the summer heat dies down. I ran 18x7.5 last year tires are just so much more money.

If you look at the 215 hankook compared to the 225 the 215 is more expensive. I will keep running the 17x7 untill next year. And then the size of the rim depends on where it ends up in st. And how wide people are finding the front can acutally go.

Quote:

Originally Posted by feldy (Post 226037)

I would just like to add to this. If you live in an area which can see a lot of rain, the star specs have been known to be vastly superior then the RS3's. Both are great tires and I've also found the RS3's to be better in the heat.

But if you have any rain, you really want the star specs. Just some food for thought. Where I live it rains quite a bit. Even in the summer.

bneale

Quote:

Originally Posted by feldy (Post 226037)

The Andy Hollis article was a great read. He recommends matching the tread width to the rim size. So for a 7" rim, I am not sure if 215 or 225 is the best tread width.

Any suggestions?

Quote:

Originally Posted by racecaresuaceb (Post 1657443)

The Andy Hollis article was a great read. He recommends matching the tread width to the rim size. So for a 7" rim, I am not sure if 215 or 225 is the best tread width.

Any suggestions?

Doesn't matter. My recommendation is if you autocross, run 225; if you track, run 215...or whatever is cheaper...LOL

How are you getting star specs( i assume you mean z2) through discount tire?

Quote:

Originally Posted by racecaresuaceb (Post 1657443)

The Andy Hollis article was a great read. He recommends matching the tread width to the rim size. So for a 7" rim, I am not sure if 215 or 225 is the best tread width.

Any suggestions?

For CS, there's a few people trying out 245's. Check out the CS discussion thread. I wouldn't daily drive 245's on a 7" wide wheel, but I do know a few that daily drive 235's and 225's.

Quote:

Originally Posted by vroom4 (Post 1657556)

How are you getting star specs( i assume you mean z2) through discount tire?

That post was from 2012.